[docs] Add sections about translation contributions (#14571)
[docs] Add sections about translation contributions (#14571)

* [docs] Add sections about translation contributions

* [docs] Be nice

* add olivier suggestions

Co-Authored-By: eps1lon <84fc128bc6cda84e77606b9e3bddd28c2b9ce031@gmail.com>

mbrookes/material-ui,kybarg/material-ui,rscnt/material-ui,callemall/material-ui,mui-org/material-ui,kybarg/material-ui,mui-org/material-ui,callemall/material-ui,mbrookes/material-ui,kybarg/material-ui,kybarg/material-ui,allanalexandre/material-ui,mui-org/material-ui,callemall/material-ui,oliviertassinari/material-ui,mbrookes/material-ui,rscnt/material-ui,lgollut/material-ui,rscnt/material-ui,oliviertassinari/material-ui,oliviertassinari/material-ui,callemall/material-ui